Ignition system



IGNITION SYSTEM Filed Sept. 13, 1935 INVENTOR A.A.'Ll SELL.

ATTORNEY Patented June 6, 1939 PATENT OFFICE IGNITION SYSTEM AlfredAubyn- Linsell, London, England, minor to Radio Corporation of America,a corporation of Delaware Application September 13, 1935, Serial No.40,364 In Great Britain September 15, 1934 2 Claims. (013123-148) Thisinvention relates to systems and apparatus for obviating disturbances inradio receivers by the ignition systems of nearby internal combustionengines and has for its object to provide 5 simple efiicient and easilyinstalled apparatus whereby the ignition systems of the internalcombustion engines of motor cars, aeroplanes, and so forth, may be"modified without serious constructional alteration or seriousinterference with their main purpose as ignition systems in such manneras to reduce or substantially eliminate their interference with nearbyradio receivers used on such vehicles.

The problem of interference with radio reiB ceivers by the ignitionsystems of internal combustion engines is a well known and seriousproblem which becomes very pressing in the case of aircraft and motorcars, and various expedients have been proposed to modify ignitionsystems so.

as to reduce or substantially eliminate such interference. Among theexpedients already proposed are the screening of those parts of theignition system likely to cause interfering radiation, another being theprovision in series in the leads to the sparking plugs and any otherignition leads (if any) likely to give rise to interfering I radiation,of damping resistances designed and intended to damp out disturbingradiation-causing oscillations. I

The principal objection to the first of the above mentioned expedientsis the considerable amount of structural alteration which is generallyinvolved if complete screening isto be obtained,

while the second expedient as utilized in known anti-interferenceignition systems of the kind whereindaniping resistances are inserted,suffers from the disadvantage that the resistances must be fairlyexpensive if they are to withstand the considerable voltage peaks towhich they are sub- 40 jected while, furthermore, they introduce ofnecessity resistance losses which may'quite seriously reduce theeffectiveness and efficiency of the ignition system as such.

The present invention provides improved means for reducing andsubstantiallypreventing the back surge of current which tends to occurin an ignition system after sparking has occurred therein, andvaccording to this invention one'or more high frequency rectiflers is orare inserted in'series in the lead of leads to those parts of anignition system where sparks occur when the system is functioning. Therectifier or rectifiers must, of course, be connected in such sense asto allow the initial flow of current to the sparking points to occur butto prevent the subsequent back surge.

The invention is illustrated in the accompanying diagrammatic drawingwhich shows one way of carrying it into effect. 8

Referring to the drawing each of the ignition leads leading from thedistributor points of the distributor of 'an internal combustionignition system to the sparking plugs of the engine includes in seriestherewith a plurality of high 10 to it as possible and the other beingadjacent the 20 sparking plug terminal and as close to that as possible.

If the rectifiers are connected in correct sense current flow in thedirection to occasion sparks at' the sparking plugs will not be reducedto any 25 substantial extent, but back surge from .the spark; ing plugswill be substantially prevented owing to the unilateral conductingproperties of the rectifiers. It is, of course, theoretically possibleto use electron discharge rectifiers in place of crystal or 30 chemicalrectifierse. g., in place of the copper oxide rectiflers alreadyreferred to-but in general, electron discharge rectifiers are notpreferred from the practical point of view for obvious reasons,principally concerned with installation maintenance and operating costs.It is also possible in some cases to use thermionic rectifiers r e. g.diodes having low temperature emitting cathodes, and in some cases heatfrom the engine, e. g., conducted from the central stem of a sparkingplug might be used to assist or cause such a cathode to become electronemissive. -As above stated, however, the use of electron-dischargerectiilers is not preferred owing to the cost and comparativecomplication involved.

Of course, where an electron discharge device -is utilized in carryingout this invention means should be provided for short circuiting it whenstarting the engine, and if desired, such short circuiting means may beprovided in association with any form of rectifier used in carrying outthis invention. Any convenient means may be provided for shortoircuiting the rectifier or rectifiers while starting the engine; forexample any short circuiting expedients or arrangements as described inmy application Serial No. 20,900, filed May 11, 1935, may be employed.Such a system is diagrammatically shown as comprising a switch S andleads l0 and II,

Although the invention provides an interference suppressor systemwhereby a high degree of suppression is obtainable without the use oiscreening means or resistances interposed-in ignition leads; the saidinvention is obviously not limited in its application to systems whereinno such screening means or interposed resistances are provided but canbe used in conjunction with the known expedients of using suppressorresistances and/or inductances and/or screening. however, the saidinvention is so used in conjunction with the said known expedients, thesuppressor resistances and/or inductances may be When,

made of lower value than would be the case where they provided as theonly means of interference suppression while similarly less extensivescreening can be employed.

' type.

ALFRED AUBYN LIN SELL.

